Ukrainian President Viktor Yanukovych has announced a reward of two million hryvni, or about $250,000, for information leading to the arrest of those responsible for four explosions in the eastern city of Dnipropetrovsk on April 27.

Yanukovych made the announcement as he visited Dnipropetrovsk on April 28 to meet with victims and oversee the investigation into what authorities have described as a "terrorist act."

Ukrainian health officials say 10 children were among the 30 people injured in the series of blasts.

They say 22 people remained hospitalized, including four who were in a grave condition.

There has so far been no claim of responsibility for the bombings, which came as Ukraine makes final preparations with Poland to co-host the 2012 European soccer championship, starting on June 8.

Dnipropetrovsk is not a host city for any of the Euro 2012 matches.

The motive for the attacks on public places was not immediately clear. Such a series of bomb blasts is considered an extremely rare occurrence in Ukraine.

Some Ukrainians say they think the blasts were aimed at discrediting the government in the eyes of the international community as the spotlight increasingly turns toward Ukraine ahead of the Euro 2012 tournament.

Others have speculated about a possible connection with the case of former Prime Minister Yulia Tymoshenko, a political opponent of Yanukovych, whose imprisonment and treatment in captivity has been condemned by Western nations.

Dnipropetrovsk is Tymoshenko’s hometown.

An Attempt To 'Destabilize' The Country

The explosions on April 27 occurred on the same day that photographs emerged showing Tymoshenko with bruises and scratches, which she says were caused by prison guards.

On April 28, a judge delayed until May 21 the start of a new trial against Tymoshenko on tax evasion charges.

The judge ruled that Tymoshenko, who launched a hunger strike on April 20 and is suffering from other ailments, is too ill to attend the proceedings.

As he met with victims in Dnipropetrovsk on April 28, Yanukovych said it was possible that a campaign had been launched to "destabilize" Ukraine.

But he gave no details about who may have been responsible, or why the perpetrators would seek to create chaos.

Yury Paramonov, a Ukrainian security official in Kyiv, downplayed the idea of links between the Dnipropetrovsk attacks and the Euro 2012 tournament.

"I think security [during Euro 2012] will be ensured," he told journalists. "We've been training for this for quite a few years already. And I would like to repeat -- one should not associate the explosions in Dnipropetrovsk with preparations for the Euro [tournament]."

Following the blasts on April 27, European soccer's governing body UEFA said it remains confident in the ability of Ukrainian authorities to stage a "smooth and festive tournament."

Hundreds of thousands of foreigners are expected to attend the event.

Prime Minister Donald Tusk of Poland, the co-host of Euro 2012, warned that the bombings must be treated "very seriously" because of the upcoming soccer tournament and because such attacks are "rather exceptional" in the region.